Improved prognosis during long-term treatment with beta-blockers after myocardial infarction: analysis of randomized trials and pooling of results.

We reviewed 14 randomized controlled trials that involved long-term treatment of patients after myocardial infarction with beta-blockers. Studies in which randomization was carried out at the time of hospital admission were excluded because of a very high rate of early withdrawal before hospital discharge. Seven studies were found methodologically acceptable, and their results were analyzed according to the "intention-to-treat" principle to avoid bias caused by late withdrawals. Although only two of the trials found a significant reduction in total deaths in the beta-blocker groups, pooling the data from all seven studies showed a highly significant treatment benefit (p less than 0.001). The best estimate of the magnitude of the reduction in mortality rates is 26%. Pooling of the data revealed similarly significant reductions in the rates of reinfarction (p less than 0.001) and sudden death (p less than 0.001).